Reefs suffering from worldwide die-off

A significant
proportion of the world's coral has died this year as a result of
the highest sea temperatures on record.

November 30,
1998
Web posted at: 11:50 AM EST

By Environmental News Network staff

"The coral reefs are the canary in the mine for global warming. They will go first,"
said Dr. Thomas Goreau in testimony at a meeting at the climate change talks
in Buenos Aires.

Goreau, a scientist working with the International Union for the Conservation of Nature, said a significant proportion of the world's coral has died this year as a result of the highest sea temperatures on record. In areas surveyed in the Indian Ocean, between 70 and 90 percent is dead, IUCN scientists said.

Reefs in tourist areas renowned for their diving opportunities, such as the Seychelles, Mauritius and the Maldives, have suffered massive die-offs. Thousands of miles of corals in the western Pacific, from Vietnam to the Philippines and Indonesia, have died or bleached as they have been starved of the symbiotic algae that provide their food and energy. The only large areas of coral to have escaped some devastation are the atolls of the central Pacific.

To highlight the economic importance of coral reefs, Gourequ noted that reefs provide more than 100 countries with fish and other services, such as tourism worth $500 billion a year. They also prevent tidal waves and erosion. And they support 93,000 fish species -- 25 percent of the total -- in 0.3 percent of its sea area.

The IUCN conclusions seem to be backed up by the results of Reef Check '97, the first global survey of human impacts on the world's coral reefs. Organized by the Institute for Environment and Sustainable Development, the survey involved more than 100 marine scientists and 750 recreational divers who surveyed 300 coral reefs in 30 countries and territories between June 15 and Aug. 31, 1997.

The Reef Check methods differ from those used in traditional ecological surveys in that they were focused specifically on detecting the effects of humans on the coral reef ecosystem. Results from about 230 sites revealed a clear pattern of global damage to coral reefs, particularly due to overfishing and destructive fishing.

Reef Check '97 teams found that the mean percentage of living coral cover on reefs was 31 percent globally, with the Caribbean recording the lowest value at 22 percent, possibly reflecting recent losses due to bleaching and diseases. The ratio of live to dead coral was highest in the Red Sea, suggesting that these reef corals are the healthiest in the world. One apparent bit of good news is that only seven sites showed greater than 10 percent cover of fleshy algae, indicating that nutrient enrichment associated with sewage pollution was not a problem at most of these "good" sites. Sewage pollution may be more important at reefs near urban areas which were not extensively studied in this survey.

Reef fish in the Indo-Pacific, seem to be hit hard. The humphead wrasse and barramundi cod were once moderately abundant on reefs, but none were reported at 85 percent of 179 reefs surveyed. Of more than 25 kilometers of Indo-Pacific reef surveyed in detail, only 26 humphead wrasse were seen. At the 125 Asian and Australian reefs surveyed, only five barramundi cod were recorded. These results suggest that cyanide and other forms of fishing have severely damaged populations of these once moderately abundant species.

High-value, edible sea cucumbers used to litter the seabed around many reefs. The three species included in Reef Check were totally absent from 41 percent of Indo-Pacific reefs surveyed, demonstrating the extent of over-harvesting. An average of 17 giant clams was found on the Indo-Pacific reefs. An indication of what natural populations used to be like was provided by the 150 to 250 giant clams recorded at several protected sites in the Red Sea and Australia.

Hong Kong provides an example of coral reefs subjected to almost every form of disturbance: overfishing, poison and dynamite fishing, pollution and sedimentation. Out of 11 collectible or edible indicator species only two (Trochus shells and butterflyfish) were recorded. Several of these once-abundant species are now effectively extinct in Hong Kong. The. Sarawak Reef Check team reported that 99 percent of the reefs have been damaged by blast fishing.

Surveys were also conducted in 1998, and the results are still being tallied. Reef Check works well as a rapid assessment tool, and indicates where additional, more detailed scientific studies are needed. It also shows the promise that can be found in the areas that have been formally protected and are showing signs of regeneration.

A joint statement was issued by IUCN's reef scientists at the Buenos Aries conference. It said: "Unless this conference takes effective action to stop global climate change, coral reefs and the benefits they provide will be condemned to death. Other ecosystems will follow."